1. Field of the Invention
The present invention relates to a thin-film magnetic head for recording which is suitable for, for example, a flying magnetic head and a contact magnetic head. More particularly, the present invention relates to a thin-film magnetic head which can produce a large magnetic field adjacent to the gap by properly preventing magnetic saturation in an upper magnetic layer, can enhance various characteristics, such as overwriting characteristics, and can enhance the controllability of the track width, and relates to a production method for the thin-film magnetic head.
2. Description of the Related Art
FIG. 30 is a partial front view showing the structure of a thin-film magnetic head (inductive head) as a related art, and FIG. 31 is a partial longitudinal sectional view of the thin-film magnetic head, taken along line XXXIxe2x80x94XXXI in FIG. 30 and viewed from the direction of the arrows.
Referring to FIGS. 30 and 31, a lower core layer 1 is made of a magnetic material, such as permalloy, and an insulating layer 9 is formed thereon.
The insulating layer 9 has a groove 9a which extends from a surface opposing a recording medium (recording-medium opposing surface) in the height direction (Y-direction in the figure) and has an inner width in the track width direction (X-direction) equal to the track width Tw.
A lower magnetic layer 3 which is magnetically connected to the lower core layer 1, a gap layer 4, and an upper magnetic layer 5 which is magnetically connected to an upper core layer 6 are formed by plating, and are stacked from the bottom in that order inside the groove 9a. 
As shown in FIG. 30, the upper core layer 6 is formed on the upper magnetic layer 5 by plating.
As shown in FIG. 31, a coil layer 7 is formed in a spiral pattern on a portion of the insulating layer 9 offset from the groove 9a in the height direction (Y-direction).
The coil layer 7 is covered with a coil insulating layer 8 made of a resist or the like, and the upper core layer 6 is placed on the coil insulating layer 8. The upper core layer 6 is magnetically connected to the upper magnetic layer 5 at a leading end portion 6a, and to the lower core layer 1 at a base end portion 6b. 
In the inductive head shown in FIGS. 30 and 31, when a recording current is applied to the coil layer 7, a recording magnetic field is induced in the lower core layer and the upper core layer 6, and a magnetic signal is recorded on a recording medium, such as a hard disk, by a leakage field produced between the lower magnetic layer 3 magnetically connected to the lower core layer 1 and the upper magnetic layer 5 magnetically connected to the upper core layer 6.
The above-described thin-film magnetic head has the following disadvantages.
That is, the lengths between the recording-medium opposing surfaces and the rear end faces in the height direction of the lower magnetic layer 3, the gap layer 4, and the upper magnetic layer 5 are all set to T1. The length T1 is called the gap depth (Gd). In the thin-film magnetic head of the related art, it is necessary to minimize T1 in order to increase the leakage magnetic flux from the gap layer 4.
As the gap depth decreases, the area of the joint surface between the upper core layer 6 and the upper magnetic layer 5 also decreases. Therefore, the magnetic flux flowing through the upper core layer 6 is condensed, and magnetic saturation occurs before the magnetic flux reaches the gap layer 4. That is, a leakage magnetic flux is also produced in the portions spaced from the gap layer 4. In particular, when the recording frequency is increased, precise recording is impossible.
Accordingly, the thin-film magnetic head has been improved, as shown in, for example, FIG. 32. FIG. 32 is a longitudinal sectional view of an improved thin-film magnetic head.
In the thin-film magnetic head shown in FIG. 32, a gap-depth defining layer 10 made of, for example, an organic insulating material is formed on a portion of a lower core layer 1 at a predetermined distance from a recording-medium opposing surface in the height direction.
A lower magnetic layer 3, a gap layer 4, and an upper magnetic layer 5 are stacked from the bottom in that order between the recording-medium opposing surface and the gap-depth defining layer 10. In FIG. 32, the gap depth (Gd) is defined by the length T2 from the recording-medium opposing surface to the position where the gap layer 4 and the gap-depth defining layer 10 contact each other, and can be easily optimized by changing the position of the gap-depth defining layer 10. Moreover, since the upper magnetic layer 5 can be made longer than the gap depth by being extended onto the gap-depth defining layer 10, the contact area between the upper magnetic layer 5 and an upper core layer 6 can be increased, regardless of the gap depth. This makes it possible to properly reduce the magnetic saturation in the upper magnetic layer 5 even when the recording density increases in future.
In order to further increase the recording density, it is necessary to increase the leakage field adjacent to the gap. For that purpose, it is preferable that the upper magnetic layer 5 have a multilayered structure composed of two or more magnetic layers, that a lower layer of the magnetic layers in contact with the gap layer 4 be formed of a high-Bs layer having a high saturation magnetic flux density Bs, and that an upper layer having a lower saturation magnetic flux density Bs than that of the high-Bs layer be formed on the high-Bs layer.
FIG. 33 is a process view of the thin-film magnetic head shown in FIG. 32. The gap-depth defining layer 10 is formed on the lower core layer 1, and the lower magnetic layer 3 and the gap layer 4 are formed on a portion of the lower core layer 1 disposed in front of the gap-depth defining layer 10 by plating. The upper magnetic layer 5 is then formed on the gap layer 4 by plating. In this case, however, a lower layer 11 of the upper magnetic layer 5 having a high saturation magnetic flux density cannot be suitably formed so as to extend onto the gap-depth defining layer 10.
This is because the gap-depth defining layer 10 is an insulating layer made of an organic insulating material or the like. Even when the lower layer 11 is formed on the gap-depth defining layer 10, the thickness thereof is much less than when formed on the gap layer 4.
An upper layer 12 formed on the lower layer 11 by plating is, of course, not easily formed on the gap-depth defining layer 10, and the thickness thereof on the gap-depth defining layer 10 is small. For this reason, the upper magnetic layer 5 formed on the gap-depth defining layer 10 is extremely thin.
In the subsequent step, the upper magnetic layer 5 is ground to line Cxe2x80x94C in order to flatten the upper surface thereof. When the thickness of the upper magnetic layer 5 at the rear end is small, as described above, the volume is substantially reduced by the grinding step, and the upper magnetic layer 5 is prone to cause magnetic saturation.
For example, when the upper magnetic layer 5 is ground to line Cxe2x80x2xe2x80x94Cxe2x80x2, a recess 5c is sometimes formed or the upper magnetic layer 5 itself is not formed at the rear end, depending on the accuracy of the flattening.
Since the lower layer 11 having a high saturation magnetic flux density formed on the gap-depth defining layer 10 is extremely thin, as described above, a magnetic flux flowing from the upper core layer 6 to the upper magnetic layer 5 is not properly guided to the lower layer 11, that is, the flow efficiency of the magnetic flux to the lower layer 11 declines. For this reason, the upper magnetic layer 5 is prone to cause magnetic saturation, and the leakage field adjacent to the gap layer 4 cannot be increased. As a result, it is impossible to produce a thin-film magnetic head which can suitably respond to future increases in recording density.
FIG. 34 is a partial plan view of the upper magnetic layer 5. The upper magnetic layer 5 is composed of a front area 5a having a width in the track width direction (X-direction in the figure) at the recording-medium opposing surface equal to the track width Tw, and a rear area 5b formed at the rear end of the front area 5a so as to gradually increase in width.
The position of a rear edge (magnetic pole edge) 5b1 of the upper magnetic layer 5 principally contributes to the overwriting characteristics, and the position of an end portion 5a, from which the width increases, principally contributes to NLTS (non-linear transition shift) and the pulse width at the 50% threshold.
As shown in FIG. 33, however, when the upper magnetic layer 5 is formed, the lower layer 11 having a high saturation magnetic density is not formed on the gap-depth defining layer 10, or the thickness of the lower layer 11 formed thereon is extremely small. The upper layer 12 formed on the lower layer 11 on the gap-depth defining layer 10 by plating is also thin. Since the upper magnetic layer 5 is thin on the rear side, and it is difficult to ensure a predetermined thickness, the positions of the rear edge 5b1 and the end portion 5a1 of the upper magnetic layer 5 are limited in order to achieve predetermined overwriting characteristics, NLTS, and pulse width at the 50% threshold. This decreases the degree of flexibility in designing the positions of the rear edge 5b1 and the end portion 5a1.
A thin-film magnetic head having the structure shown in FIG. 35 has also been proposed. FIG. 35 is a partially enlarged longitudinal sectional view showing only the portions near the recording-medium opposing surface. In the thin-film magnetic head shown in FIG. 35, a lower magnetic layer 3 is formed on a lower core layer 1 by grinding the lower core layer 1 so as to form a step. A gap layer 13 is placed on the lower magnetic layer 3. The gap layer 13 is made of an insulating material, such as Al2O3 or SiO2. A gap-depth defining layer 10 is formed on the gap layer 13 at a predetermined distance from the recording-medium opposing surface. The gap depth is determined by limiting the rear end in the height direction of the joint portion between the gap layer 13 and an upper magnetic layer 5 by a front end face of the gap-depth defining layer 10 on the side of the recording-medium opposing surface. In FIG. 35, the gap depth is designated by L3.
The upper magnetic layer 5 is formed on the front end face of the gap-depth defining layer 10 and on a portion of the gap layer 13 between the gap-depth defining layer 10 and the recording-medium opposing surface with a seed layer 5d therebetween. The upper magnetic layer 5 is magnetically connected to an upper core layer 6 on the upper surface thereof.
In this thin-film magnetic head, since the lower magnetic layer 3 is formed by grinding the lower core layer 1 by, for example, ion milling, magnetic powder due to the grinding adheres onto both side faces in the track width direction (X-direction) of the upper magnetic layer 5. The track width Tw determined by the width in the track width direction of the upper magnetic layer 5 is increased due to the adhering magnetic powder, and this makes it difficult to produce a thin-film magnetic head which can achieve a narrower track width.
In order to remove the magnetic powder, the upper magnetic layer 5 must be subjected to ion milling from both side directions. This complicates the production process, and the height of the upper magnetic layer 5 is reduced by ion milling. As a result, it is difficult to properly remove the magnetic powder, and the controllability of the track width is substantially reduced.
Accordingly, the present invention aims to overcome the above problems in the related art, and an object of the invention is to provide a thin-film magnetic head which can produce an appropriate magnetic field adjacent to the gap by properly preventing magnetic saturation in an upper magnetic layer, can enhance various characteristics, such as overwriting characteristics, and can enhance the controllability of the track width, and to provide a production method for the thin-film magnetic head.
In order to achieve the above object, according to an aspect of the present invention, there is provided a thin-film magnetic head including a lower core layer; a magnetic pole section having a lower magnetic layer, a gap layer, and an upper magnetic layer stacked in that order on the lower core layer, the upper magnetic layer having a width in the track width direction less than that of the lower core layer so as to determine the track width; and an upper core layer formed on the upper magnetic layer, wherein a gap-depth defining layer is formed on a portion of the lower core layer behind a surface opposing a recording medium in the height direction, the lower magnetic layer extends from the opposing surface to a front end face of the gap-depth defining layer on the side of the opposing surface, a metal film is formed on a portion of the gap-depth defining layer disposed behind a contact face between the lower magnetic layer and the gap-depth defining layer in the height direction, the gap layer is formed on the lower magnetic layer so as to be in contact with at least the gap-depth defining layer, and the upper magnetic layer extends over the gap layer and the metal film.
In the thin-film magnetic head, the metal film is formed on a part of the upper surface of the gap-depth defining layer. The lower magnetic layer is formed on the lower core layer so as to extend between the opposing surface and the front end face of the gap-depth defining layer, and not to extend onto the metal film which is formed on the upper surface of the gap-depth defining layer.
The gap layer is made of a material which can be plated, and the gap layer and the metal film formed on the gap-depth defining layer serve as a seed layer for the upper magnetic layer which is formed on the gap layer by plating.
For this reason, it is possible to suitably form the upper magnetic layer over the gap layer and the metal film by plating, and to form the upper magnetic layer with a predetermined thickness on the gap-depth defining layer.
Consequently, the contact area between the upper magnetic layer and the upper core layer can be increased, the volume of the upper magnetic layer can be sufficiently increased, and magnetic saturation in the upper magnetic layer can be properly reduced even when the recording density increases in future.
Since the upper magnetic layer having a predetermined thickness can be formed on the metal film disposed on the gap-depth defining layer, the positions of the end portion, from which the width increases in width in the height direction, and the rear edge of the upper magnetic layer on the rear side can be freely designed and changed in order to optimize the overwriting characteristics, NLTS, and the pulse width at the 50% threshold.
Since the rear end of the upper magnetic layer disposed on the gap-depth defining layer have a sufficient volume, the upper magnetic layer can be formed in a predetermined shape without being affected by the accuracy of flattening.
The thin-film magnetic head of the present invention includes the lower magnetic layer, and the lower magnetic layer is not formed by grinding the lower core layer, as shown in FIG. 35. Therefore, it is not necessary to remove magnetic powder adhering onto side faces of the upper magnetic layer in the track width direction, and the controllability of the track width can be made higher than before.
Preferably, the upper magnetic layer has a layered structure composed of two or more magnetic layers, the lowermost layer of the magnetic layers in contact with the gap layer is formed of a high-Bs layer having a higher saturation magnetic density than those of the other magnetic layers, and the high-Bs layer is formed over the gap layer and the metal film.
Since the lowermost layer (high-Bs layer) having a high saturation magnetic flux density is also formed onto the metal film disposed on the gap-depth defining layer, it can be made thick on the gap-depth defining layer. The magnetic flux flowing from the upper core layer to the upper magnetic layer can be properly guided to the high-Bs layer of the upper magnetic layer disposed on the gap-depth defining layer, and the flow efficiency of the magnetic flux can be enhanced. This can increase the leakage magnetic flux adjacent to the gap. As a result, it is possible to produce a thin-film magnetic head which can suitably respond to future increases in recording density.
Preferably, the front end face of the gap-depth defining layer is a curved face or an inclined face which is inclined in the height direction away from the lower core layer toward the upper core layer.
For example, the cross section of the gap-depth defining layer in the height direction is substantially semielliptical or substantially trapezoidal.
The front end face of the gap-depth defining layer may be a vertical face which vertically rises from the lower core layer toward the upper core layer.
Preferably, the gap-depth defining layer is made of an organic material. For example, the gap-depth defining layer is made of a resist material.
The gap-depth defining layer may be made of an inorganic material.
Preferably, the metal film is made of a nonmagnetic metal material. In this case, it is preferable to select as the nonmagnetic metal material at least one of Au, Cu, Cuxe2x80x94Ni, Pt, and Ti.
The metal film may be made of a magnetic metal material. It is preferable to make the metal film of a nonmagnetic metal material rather than of a magnetic metal material. This is because the metal film made of the magnetic metal material may melt when the upper magnetic layer is formed thereon by plating.
Preferably, the metal film made of the nonmagnetic metal material or the magnetic metal material is formed by sputtering. This allows the metal film to be more accurately formed on the gap-depth defining layer.
Preferably, the metal film is formed by placing a nonmagnetic metal film on an underlying film made of the nonmagnetic metal material or the magnetic metal material.
This structure is effective particularly when the gap-depth defining layer is thin. When the gap-depth defining layer is thin, the distance between the upper magnetic layer formed thereon and the lower core layer formed thereunder is reduced, and the magnetic field is prone to leak between the upper magnetic layer and the lower core layer. This reduces the leakage field produced from the surface opposing the recording medium adjacent to the gap.
Since the nonmagnetic metal film is formed by plating, it can be made thick. By forming a thick nonmagnetic metal film formed by plating on the underlying film made of, for example, a nonmagnetic metal material and formed on the gap-depth defining layer by sputtering, an appropriate distance can be ensured between the upper magnetic layer formed on the gap-depth defining layer and the lower core layer formed under the gap-depth defining layer. This can reduce the leakage field between the upper magnetic layer and the lower core layer.
Preferably, the nonmagnetic metal film is made of at least one of NiP, NiPd, NiW, NiMo, Au, Pt. Rh, Pd, Ru, Cr, and Ti. Using these materials makes it possible to suitably form a highly heat-resistant and highly adhesive nonmagnetic metal film.
The magnetic pole section may be composed of two layers, that is, the gap layer and the upper magnetic layer, and the gap layer may be formed on the lower core layer so as to extend between the opposing surface and the front end face of the gap-depth defining layer.
The gap layer may extend from the opposing surface onto at least a part of the metal film formed on the gap-depth defining layer, and the upper magnetic layer may be formed on the gap layer placed on the metal film.
Preferably, the gap layer is made of a nonmagnetic metal material, and at least one of NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, Cr, and Ti is selected as the nonmagnetic metal material.
According to another aspect of the present invention, there is provided a thin-film magnetic head production method including the steps of: (a) forming a gap-depth defining layer, which has a curved surface and is substantially semielliptical in cross section in the height direction, on a lower core layer at a predetermined distance in the height direction from a surface opposing a recording medium; (b) forming a metal film over the lower core layer and the gap-depth defining layer; (c) covering a portion of the metal film formed on the upper surface of the gap-depth defining layer with a resist layer, and removing the other portion of the metal film which is not covered with the resist layer so that at least a front end face of the gap-depth defining layer on the side of the opposing surface is not covered with the metal film; (d) forming a lower magnetic layer on the lower core layer by plating so as to extend between the opposing surface and the front end face of the gap-depth defining layer; and (e) forming a gap layer on the lower magnetic layer by plating, and then forming an upper magnetic layer over the gap layer and the metal film remaining on the upper surface of the gap-depth defining layer by plating.
Through the above steps, the metal film can be easily and reliably formed on the curved upper surface of the gap-depth defining layer. In the step (d), the lower magnetic layer can be formed by plating so as to extend from the opposing surface to the front end face of the gap-depth defining layer offset from the metal film toward the opposing surface and so as not to extend onto the metal film disposed on the gap-depth defining layer.
In the step (e), after the gap layer is formed on the lower magnetic layer by plating, the upper magnetic layer can be formed over the gap layer and the metal film by plating. Therefore, the upper magnetic layer with a predetermined thickness can be formed on the gap-depth defining layer.
The production method of the present invention may include the following steps, instead of the above steps (b) and (c):
(f) covering portions of the gap-depth defining layer other than an upper surface with a resist layer, and forming a metal film on the upper surface of the gap-depth defining layer which is not covered with the resist layer; and
(g) removing the resist layer so that at least a front end face of the gap-depth defining layer on the side of the opposing surface is not covered with the metal film.
These steps also allow the metal film to be suitably and easily formed on the upper surface of the gap-depth defining layer.
The production method of the present invention may include the following steps, instead of the above steps (a) to (c):
(h) forming a gap-depth defining layer over the entire surface of a lower core layer, and forming a metal film on the gap-depth defining layer;
(i) forming a resist layer having a predetermined length in the height direction on a portion of the metal film disposed behind a surface opposing a recording medium in the height direction, and removing the other portion of the metal film which is not covered with the resist layer; and
(j) removing the resist layer, and removing a portion of the gap-depth defining layer which is not covered with the metal film by using the metal film as a mask so that the gap-depth defining layer of substantially rectangular or substantially trapezoidal cross section in the height direction remains under the metal film.
The above production method makes it possible to make the cross section of the gap-depth defining layer substantially rectangular or substantially trapezoidal.
The production method of the present invention may include the following steps, instead of the above steps (h) and (i):
(k) forming a gap-depth defining layer over the entire surface of a lower core layer, covering the gap-depth defining layer with a resist layer, and forming a hole having a predetermined length in the height direction in a portion of the gap-depth defining layer disposed behind a surface opposing a recording medium in the height direction; and
(l) forming a metal film on a portion of the gap-depth defining layer which is exposed through the hole.
This also makes it possible to easily and suitably form a gap-depth defining layer of substantially rectangular or substantially trapezoidal cross section.
The production method of the present invention may include the following steps, instead of the above steps (a) to (c):
(m) forming a gap-depth defining layer over the entire surface of the lower core layer, and forming an underlying for a metal film on the gap-depth defining layer;
(n) covering the underlying film with a resist layer, forming a hole having a predetermined length in the height direction in a portion of the resist layer disposed behind a surface opposing a recording medium in the height direction, and forming a nonmagnetic metal film on a portion of the underlying film exposed through the hole by plating; and
(o) removing the resist layer, and removing portions of the underlying film and the gap-depth defining layer which are not covered with the nonmagnetic metal film so that the underlying film and the gap-depth defining layer of substantially rectangular or substantially trapezoidal cross section in the height direction remain under the nonmagnetic metal film.
In these steps, the metal film can be formed with a two-layer structure composed of the underlying film and the nonmagnetic metal film formed thereon. Since the nonmagnetic metal film can be made thick, the metal film including the nonmagnetic metal film formed by plating is effective in reducing the magnetic field leaking between the upper magnetic layer formed on the gap-depth defining layer and the lower core layer formed under the gap-depth defining layer, in particular, when the gap-depth defining layer is thin.
Preferably, in the above step (e), the upper magnetic layer is formed by plating so as to have a layered structure including two or more magnetic layers, the lowermost layer of the magnetic layers in contact with the gap layer is formed of a high-Bs layer having a higher saturation magnetic flux density than those of the other layers, and the high-Bs layer is formed over the gap layer and the metal film formed on the gap-depth defining layer by plating.
Since the metal film is formed on the upper surface of the gap-depth defining layer, the lowermost layer (high-Bs layer) of the upper magnetic layer having a high saturation magnetic flux density can be suitably and easily formed thereon with a predetermined thickness by plating.
Preferably, the gap-depth defining layer is made of a resist material, and is cured by heat treatment in the above step (a), (h), (k), or (m).
Preferably, the metal film or the underlying film in the above step (b), (f), (h), (l), or (m) is formed by sputtering. This allows the metal film to be suitably formed on the gap-depth defining layer.
Preferably, the nonmagnetic metal film in the above step (n) is made of at least one of nonmagnetic metal materials NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, Cr, and Ti by plating.
Preferably, the gap layer in the above step (e) is made of at least one of nonmagnetic metal materials NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, Cr, and Ti by plating.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.